The invention relates to an illumination instrument for generating light and dark field illumination wherein an optical component is mounted in one area where the bundles of rays for light field and dark field illumination pass separately through different zones. This component has a different index of refraction in the inner zone that is traversed by the light field bundle than in the outer zone that is traversed by the dark field bundle. A stop that is switchable is provided in the vicinity of the component in order to suppress the light field bundle or beam.
Instruments known to date and related to incident light dark and light field illumination and of the design disclosed above and in German Published Application No. 2,021,784 so far have been designed and built only as accessory components to microscopes equipped with revolving objective nosepieces, or, as regards special microscopes, they are solidly built into the objective nosepiece.
Attempts have recently been undertaken to equip small single microscopes also with supplementary incident light illumination devices. However, because of design bulk requirements it has proved possible so far to create only light field incident light illumination. To that end, an appropriate device was locked between the ocular tube and the saddle bracket. The dark field beam which necessarily is made to pass outside the microscope objective, could not be made to pass by means of the previously known imaging methods for a dark field through the apertures present in the saddle bracket and in the fixed objective nose.
The invention therefore has as an objective the problem of creating an incident light illumination device or instrument by means of which a dark field beam may be made to pass through a relatively elongated and narrow cylindrical aperture above a microscope objective.